1. Field of the Invention
This invention relates to an applying implement which contains an application fluid, such as correction liquid, and applies it onto an application surface.
2. Description of the Prior Art
There has been conventionally known an applying implement equipped with a valve mechanism which allows an application fluid to be applied on an application surface even if the application fluid has a large viscosity as a correction liquid. For example, Unexamined Japanese Utility Model Publication No. HEI 2-48172 discloses such an applying implement.
FIG. 10 shows a conventional applying implement, wherein a structure of a head portion (a lower portion in the drawing) is shown in detail. In the drawing, a main body 90 of the applying implement is secured with a head cylinder 92. The head cylinder 92 includes a front end wall 91 provided at the front end thereof. The front end wall 91 has a through hole 93 opened in the central portion thereof.
The head cylinder 92 accommodates a shaft 94 therein so as to allow the shaft 94 to shift in an axial direction of the applying implement (i.e. in the up-and-down direction in the drawing). A pen tip (i.e. an application tip) 95 is securely fixed to the front end of the shaft 94. A spring 96 is provided between the pen tip 95 and the main body 90 so as to urge the pen tip 95 forward (i.e. downward in the drawing). The pen tip 95 chiefly consists of a head portion 95a and a tail portion 95b. The head portion 95a has a diameter smaller than that of the through hole 93 so that it can protrude out of the bead cylinder 92. The tail portion 95b bas a diameter larger than that of the through hole 93. There is provided a convex spherical surface 97 between the head portion 95a and the tail portion 95b. This convex spherical surface 97 serves as a shoulder abutting the inside surface of the front end wall 91 around the through hole 93. The inside surface of the front end wall 91 is a concave spherical surface 98 having a radius of curvature larger than that of the convex spherical surface 97. Thus, the convex spherical surface 97 and the concave spherical surface 98 come into contact with each other around the through bole 93 so as to define a seal between the bead cylinder 92 and the pen tip 95.
Namely, when no external force is applied against the pen tip 95, the spring 96 urges the pen tip 95 to extend forward (i.e. downward in FIG. 10) and therefore the convex spherical surface 97 is pressed to fit to the concave spherical surface 98. Thus, the through hole 93 is completely closed. On the contrary, if the pen tip 95 is pressed against paper or the like material for application of fluid, the pen tip 95 receives a reaction force and retracts inward together with the shaft 94 against the resilient force of the spring 96. This retracting motion of the pen tip 95 and the shaft 94 causes application fluid in the head cylinder 92 to flow forward beyond the clearance between the convex spherical surface 97 and the concave spherical surface 98. And, after passing through the through hole 93, the application fluid is extracted out of the head cylinder 92 and is then supplied onto the paper or the like application surface.
However, such a conventional applying implement shown in FIG. 10 has problems as described below.
(a) Recently, there has been increasing a need of developing an applying implement which allows an application fluid to be accurately applied within a limited small area. In order to realize such a fine application of fluid to a very small area, it is needless to say that the radius size of the pen tip 95 must be reduced. Furthermore, it is essential to reduce the radius size of the head cylinder 92 because an application area must be seen by an operator during the application of fluid without being hidden behind the head cylinder 92. For this reason, these components 92 and 95 will be required to be made of a hard material such as metal, and ceramic or other inorganic material.
However, if the head cylinder 92 and the pen tip 95 are both made of hard materials, the seal between the convex spherical surface 97 and the concave spherical surface 98 will be worsened because contact of two hard materials usually provides poor sealing ability. Requirement of accuracy to the convex spherical surface 97 and the concave spherical surface 98 may be enhanced for increasing the sealing ability but would be accompanied with an increase of cost.
(b) As the pen tip 95 itself serves as a valve, it tends to allow foreign particles such as dirt or dust to enter inside the head cylinder 92 beyond the sealing part. This foreign particles become the case of further deteriorating the sealing ability. Especially, in the case where the convex spherical surface 97 and the concave spherical surface 98 are both made of hard materials, the seal ability will be greatly lowered even if an entering foreign particle is very small.
(c) If the application fluid has too large viscosity to freely drop or come out of the head cylinder 92 upon opening the sealing part at the pen tip 95, the main body 90 of the applying implement will be generally squeezed to forcibly extract the fluid. Such a forcible extraction, however, makes it difficult to finely adjust the application fluid amount to be supplied because a large amount of fluid is likely to come out of the through hole 93 at a time.
(d) When pressed against paper or the like material, the pen tip 95, if made of hard material, normally transmits a reaction force directly to a user's hand. Therefore, no comfortable feeling will be enjoyed when used.